There is a buckle including a pair of side frame portions, and a first crossbar and a second crossbar ranged between the pair of side frame portions. The buckle is provided with the fastening portion fastening the belt-like body when the belt-like body is wound around the first crossbar in such a way that once the belt-like body is inserted to pass between the pair of side frame portions from a back surface side, and is pulled out of a front surface side, the belt-like body is pulled out of the back surface side again by passing between the first crossbar and the second crossbar. (See Patent Document 1 and Patent Document 2)
Such buckle includes a function in which the more a tensional force acts on the belt-like body which has been inserted to pass through, the more a fastening force relative to the belt-like body is strengthened. On the other hand, in such buckle, if the tensional force acting on the belt-like body stops, or has been reduced, the second crossbar is not strongly pressed against a pulled-out portion of the belt-like body so as to become a state wherein a variation in a fastening position relative to the belt-like body can occur. Typically, if the belt-like body fastened to the buckle, and tightening a specific portion (for example, a hip or a chest) of a body or a specific portion (for example, a bag portion of a backpack) of an article, moves from the specific portion by walking, transportation, and the like to thereby cause a slight loosening in the belt-like body, the fastening position of the buckle relative to the belt-like body varies to cause further loosening in the belt-like body.